In semiconductor integrated circuits, refinement and integration have been developed, and accuracy in photolithographic apparatus as a technology for forming patterns has been increased to achieve micromachining by the apparatus. The photolithographic technology, however, has almost reached a limit by that the machining accuracy required has get close to the diffraction limit of exposure light.
In order to further promote refinement and high accuracy, proposed is a photo-nanoimprint method, where a mold having a fine pattern of protrusions and depressions is pressed to a resist that has been applied to a substrate to transfer the pattern of the mold to the resist film on the substrate.
In particular, special attention has been given to a photo-nanoimprint method for producing a fine resist pattern on a substrate by pressing a mold transparent against exposure light to a photo-curable composition applied onto a substrate, curing the photo-curable composition by light irradiation, and detaching the mold from the cured product.
The photo-nanoimprint method, however, has a problem that a large mold-releasing force is necessary for releasing the mold from the cured product. In some cases, the large mold-releasing force causes defects in the pattern or reduces the accuracy in alignment by floating of the substrate from the stage on which the substrate placed.
Against such a problem, PTL 1 describes a method for reducing the mold-releasing force by generating a gas between a mold and a resist by adding a gas-generating agent that generates a gas by means of light or heat to a photo-curable composition.
PTL 2 describes a method for generating a gas between a mold and a resist by placing a photocatalyst on the surface of the mold and performing light irradiation to decompose the resist being in contact with the mold through oxidation by the photocatalyst.
In the method described in PTL 1, since the photo-curable composition contains the gas-generating agent, bubbles are easily generated in the cured product by the generation of a gas.
In the method described in PTL 2, since the gas is generated by directly oxidizing the surface of a photo-cured product to decompose it, the surface of the photo-cured product is substantially deteriorated.
That is, the above-described two methods hardly increase the accuracy in pattern prepared as a cured product.